Solar Power Generation Capability and Three-Port Converters for PV-Battery Powered Applications

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Solar energy is one of the most useful sources of sustainable energy. Intermittency negatively affects the efficiency and reliability of solar power. To mitigate such a problem, a power electronic converter is used to enhance the solar power generation capability, such as detecting faulty solar photovoltaic (PV) cells to be eliminated from the solar system or tracking the maximum power point (MPPT). Other advantages of power converters are integrating energy storage systems (ESS) with the solar energy system and managing power flow. Solar cell power performance is greatly affected by two critical factors, aging and cracks. In order to mitigate their negative effects on the solar system, these cells are to be substituted by new cells; therefore, replacing the solar panels. In this research, an active crack detection method is proposed that can detect the cracked cells within a solar string by using AC parameter characterization without a need to have a physical inspection. In this research, an analog voltage-based MPPT algorithm for individual PV module is proposed and experimentally verified. The maximum power points of solar cell can be joined by an approximately linear line. The slope of this line varies depending on the type and characteristic of the panels. Utilizing this characteristic, a bipolar junction transistor (BJT) is used to implement a variable voltage reference as the DC load line of the BJT can be designed to match the MPP line of the PV panel. This improves the accuracy of the maximum power point reference voltage without the need for a digital controller or PID controller. This research also proposes two novel compact three-port converters. The proposed converters are used to interface a PV module, battery and load. The proposed converters are able to achieve MPPT, battery power management and output voltage regulation simultaneously. The first converter can be used for a stand-alone system or in a microgrid structure. The second converter is useful when bidirectional power flow is needed at the output port for some applications, such as grid-connected solar system and electric vehicle where regenerative braking is used. Each converter combines three converters to form one integrated converter by sharing some components such as switches, inductors and capacitors. Thus, the converters have a high power density and fewer components compared to the traditional DC-DC converters. The integrated PV-battery system is the promised solution for both intermittency and the unpredictable load demand.
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